The present invention relates to a sealing assembly for molds used in the manufacture of sanitary fixtures such as bidets, toilets, and the like.
Sanitary fixtures can be produced using suitable compound molds comprising a series of complementary parts which are made of a porous substance permeable to water, such as plaster of Paris or synthetic resins. The parts or dies are capable of being assembled to define a molding cavity into which is introduced a slip which is a ceramic material in an aqueous suspension. A typical mold for casting fixtures comprises a lower die, also known as a foot, two symmetrical lateral dies capable of mating with the foot to create the molding cavity, and an upper die, also known as a piston, which is capable of closing and completing the cavity. The two lateral dies define the outer surface of the item to be molded. The foot and the piston are provided with projecting elements or cores which are capable of defining the internal cavities of the item, such as the bowl and support foot cavity of a bidet.
Problems have arisen during usage of such molds from improper mating or sealing between the mutual contact surfaces of the mold dies. Specifically, if the mutual contact surfaces do not fit together perfectly, cracks will be present between the mold parts through which slip will escape, causing losses of material and surface defects in the parts. Such problems assume particular importance when the molds are used in pressure-type casting facilities, where the slip is introduced between molds at a relatively high pressure, such as for example, at 3 to 4 atmospheres of pressure.
According to prior art methods, sealing between the mating surface of the piston and the corresponding mating surfaces of the lateral dies of the molds is achieved by means of a gasket. The gasket is partly accommodated in a respective peripheral seat which is recessed into the mating surface of the piston, and which projects beyond the mouth of the seat in order to produce the seal with the mating surfaces of the lateral dies when the mold is assembled. However, this solution has proven unsatisfactory due to the fact that such gaskets become damaged and worn relatively quickly due to friction against the mutually mated surfaces of the lateral dies during insertion and extraction of the piston into and out of the latter.
It is therefore desirable to provide a sealing assembly for molds which is resistant to wear and corrosion.